Europol, the European Union's joint police, says there are more than 680 'suspicious games' dating to 2008, including a Champions League matchup and three World Cup qualifiers.

Soccer is the world's most popular sport. And now, after an 18-month investigation into game-fixing, it appears as if it's one of the world's most corrupt sports as well.

Europol, the European Union's joint police body, said Monday that its wide-ranging investigation uncovered more than 680 "suspicious games" on five continents, among them a Champions League game in England that ended in a tie and three World Cup qualifiers, two played in Africa and the other in Central America.

Europol declined to name specific suspects, teams or games because investigations are continuing, but the suspicious Central American game featured teams from CONCACAF, the regional federation that includes the United States.

A U.S. Soccer spokesman said Monday that the organization has not been made aware of any investigation into games involving the American team, although Europol investigators said there was at least one questionable result in Canada, which is also a CONCACAF member.

Europol said 425 people, including game and club officials, players and criminals, from at least 15 countries were involved in fixing games in Europe alone dating to 2008. A Singapore-based crime network was at the center of the Europol probe, which uncovered $10.9 million in betting profits and $2.7 million in bribes, with some of the bribes topping $135,000.

"This is a sad day for European football," Rob Wainwright, the head of Europol, said during a news conference in The Hague. "It is clear to us this is the biggest-ever investigation into suspected match-fixing in Europe. It has yielded major results, which we think have uncovered a big problem for the integrity of football in Europe."

It has been estimated that about $1 trillion is wagered annually on international sports contests, so game-fixing in soccer is hardly new.

FIFA, the sport's international governing body, last month barred 41 players for fixing games in South Korea and the president of the South African association was suspended in December after it was learned that four exhibition games preceding the 2010 World Cup were fixed. And last summer, Italy's top-tier professional leagues were clouded by a wide-ranging scandal that involved some of the biggest names and clubs in the country.

But what makes the Europol probe especially noteworthy is the scope of the corruption, with investigators identifying dozens of suspicious games in Turkey, Germany and Switzerland, among others.

German investigator Friedhelm Althans said the new findings were just "the tip of the iceberg," and Wainwright said the probe uncovered wrongdoing "on a scale and in a way that threatens the very fabric of the game."